Age among women and men, time to pregnancy and risk of miscarriage

Older age of women is strongly associated with reduced fertility and early pregnancy complications. These associations might also be present across the full range of reproductive age of both women and men. We assessed the associations of age of women and men with time to pregnancy and miscarriage risk.

This population-based prospective cohort study was conducted in Rotterdam, the Netherlands. A total of 3604 women and their partners were included from the preconception period onwards with follow-up until birth. For this study, participants were followed until conception or 22 weeks of pregnancy for the time to pregnancy and miscarriage analyses, respectively. Outcomes included fecundability, defined as the per-month probability of conceiving; infertility, defined as a time to pregnancy or duration of pursuing pregnancy of more than 12 months or use of assisted reproductive technology; and miscarriage, defined as pregnancy loss before 22 weeks of gestation.

In total, 18.1% of the population was infertile and 12.7% of all recognized pregnancies led to a miscarriage. As compared to women aged 30.0-34.9 years, those aged < 25.0, 25.0-29.9, and ≥ 40.0 years had increased odds of infertility (odds ratio (OR) 2.14 (95% confidence interval (CI), 1.60-2.87); OR 1.27 (95% CI, 1.05-1.53); and OR 2.00 (95% CI, 1.05-3.80), respectively). Women aged 35.0-39.9 years had no increased odds of infertility. Similar results were observed for fecundability. As compared to women aged 30.0-34.9 years at conception, those aged 35.0-39.9 and ≥ 40.0 years had strongly increased odds of miscarriage (OR 2.03 (95% CI, 1.51-2.72) and 4.24 (95% CI, 2.45-7.36), respectively). As compared to men aged 30.0-34.9 years, those aged < 25.0 years had lower fecundability (fecundability ratio (FR) 0.71 (95% CI, 0.58-0.87)). As compared to men aged 30.0-34.9 years, those aged ≥ 40.0 years had the highest odds of miscarriage (OR, 2.09 (95% CI, 1.39-3.14)).

Age among both women and their partners is a strong risk factor for adverse fertility and early pregnancy outcomes. Strategies optimizing age at which couples start family planning, focusing on both women and men, will have a great individual and public health impact.